Original topic:

Problem with multichannel PCM audio on Q930C

(Topic created on: 02-05-2024 06:37 PM)
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Hello There is a problem with the way my Samsung HW-Q930C soundbar system plays back Multi Channel PCM audio.

I am trying to play a Super Audio CD in my Blu-ray/SACD player that is connected to the HDMI input of the soundbar. The player is set to convert the DSD format to multi-channel PCM that is then sent to the soundbar by an HDMI cable. I understand the soundbar doesn't play back DSD, so I have set my Blu-ray player to send multi channel PCM which is supported.

The SACD discs I am having trouble with are 1970s Quadraphonic recordings that have 4 audio channels (Front Left, Front Right, Back Left, Back Right), however, the SACD discs are encoded as 5.0 channels because they include a silent Front Centre channel. When I play back one of these 4 channel 5.0 format discs, no sound comes from the Back Right surround speaker of my Q930C system. I think this is because the silent centre channel on the disc is wrongly directed to the Back Right speaker , so that speaker doesn't play any sound. The blue light on the back of the speaker is on, which suggests the speaker is active, but it is playing silence.

I have tried different settings including Standard and Surround, but this does not fix the problem. It seems the actual problem is that the soundbar is only playing back the first 4 channels because it 'assumes' they all contain audio, but one of the channels (Front Centre) is silence, while the actual Back Right track is not played.

I have extracted the audio from the disc to get a better understanding of what the problem is. If I playback the file from a USB drive through my Blu-ray player I have the same problem, the Back Right channel is silent. However, if I edit the file to add a silent .1 subwoofer/Low Frequency Effects track, thus turning the 5.0 file into a 5.1 file, the audio plays correctly, with the Back Right channel playing sound.

Here is a 5.0 multi-channel FLAC file I created from the SACD that has not been fixed. This file doesn't play properly. https://1drv.ms/u/s!AjuP8f7DgnZEhKVVvCl1fBpvlrclkQ?e=wWOK5T If I open this multi-channel FLAC file in Audacity, I can see that the 3rd track is the silent Centre channel track. It seems to me that this track is being sent to the Back Right speaker, while the fourth track is being sent to the Back Left speaker. 

Here is a 5.1 multi-channel FLAC file that I edited to convert the  5.0 4 channel file to 5.1 channels This file plays correctly with the Back Right channel playing properly. https://1drv.ms/u/s!AjuP8f7DgnZEhKVW1fKl0TWkWy2DcQ?e=Ax53S7

It seems with a 5.1 file (or just directly playing back a SACD encoded as 5.1) the soundbar understands the correct channel layout. But when receiving 4 audio channels in a 5.0 disc (or a file version of the same) the soundbar doesn't understand the correct layout of the channels, and thus the silent centre channel is sent to the Back Right speaker which is thus silent.

Can this problem please be investigated, because I feel it would be possible for there to be a firmware update to my soundbar to make it properly recognise the correct channel layout when playing back multi-channel files; including this issue of 4 tracks (Front Left, Front Right, Back Left, Back Right) that are in a 5.0 file with a silent Front Centre track.

Perhaps another option is to update the Q930C profile in the Samsung things app so that channels can be moved when playing back audio? But the first option of fixing the multi-channel PCM playback on the soundbar itself would be much preferred as this wouldn't require any user intervention to fix the channel layout.

Please note that I have not been able to stream the FLAC file to the soundbar using Airplay or Bluetooth. Both of these protocols seem to mix down the file to stereo, and thus the soundbar only plays with both of the rear speakers not playing any sound. To play the FLAC files I have provided to you you need to use a media play or Blu-ray player that can play back multi-channel FLAC files. If you do this test yourself you will find that the original 5.0 file does not work properly but the 5.1 file I have created works.

Please forward this information to the engineering team that works on your sound bars. I appreciate the issue I am having is of a technical nature that not everyone will understand, but I am hopeful that this could be fixed by changing the way the soundbar understands channel layouts. As it stands, I can only playback my 4 channel (Quadraphonic) SACDs from files that I manually fix by adding a silent 0.1 channel instead of just playing the discs. This is very disappointing given how much I spent on the soundbar system. 

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